Resumen

RAMIREZ-CAMPOS, Marcela  y  VILLAFUERTE-ROBLES, Leopoldo. Effect of Formulation Variables on Verapamil Hydrochloride Release from Hydrated HPMC Matrices. Rev. Soc. Quím. Méx [online]. 2004, vol.48, n.4, pp.326-331. ISSN 0583-7693.

Among different variables that influence drug release from hydrated hydrophilic matrices, the polymer proportion, the drug dose and the matrix pH can be included. In a first approach to formulate a transdermal drug delivery system, these variables have been used to modify the drug release rate and to examine its effect on the release mechanism. Hydrated matrices were prepared varying the matrix proportion of hydroxypropyl methylcellulose (HPMC), the pH and the amount of verapamil hydrochloride loaded. The matrices release behavior (USP 23 apparatus 5, paddle over disk method, at 150 rpm) was examined using 900 mL of an aqueous solution of NaCl (0.9%) as dissolution medium. The increase of the HPMC matrix proportion reduced the release rate of the drug. The release profiles showed zero order kinetics for drug dissolution proportions up to 70%. The increase of the matrix drug load increases slightly the release rate. The increase of the matrix pH from 5.0 to 8.0 increased the release rate. The effect of both pH and drug load becomes lesser as the matrix polymer proportion increases from 5% to 15% w/w. The use of a Collodion membrane covering the hydrated matrices decreases two orders of magnitude the release rate of verapamil hydrochloride.

Palabras llave : Sustained release; verapamil; transdermal delivery; HPMC; pH.

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